1. Field of the Invention
This invention relates to a motor control device for a radio control system which is adapted to determine a switching level of rotational direction of a servomotor mounted on a controlled object as desired, and more particularly to a motor control device which is adapted to set an inversion level of the servomotor depending upon a type of the controlled object such as, for example, a racing type model car, a buggy type model car or the like in remote control of the controlled object to adjust a control range in each of forward, braking and backing of the object as desired.
2. Description of the Prior Art
A radio control system is to cause a receiver mounted on a controlled object such as, for example, a model car or a model plane, or an industrial equipment such as a crane, pump or the like to receive and demodulate radio wave transmitted from a transmitter, to thereby control a rotation angle of a servomotor mechanically connected to an operation section of the controlled object.
The typical radio control system which has been conventionally employed will be described hereinafter with reference to FIGS. 3 to 6.
In the conventional radio control system, a channel signal transmitter A is provided on a transmitter side as shown in FIG. 3, which includes a variable resistor 1 connected between a voltage source VB and a ground VS having a slider element 1a connected to a control element 1b, an operational amplifier 3 having an inversion input terminal connected to the slider element 1a and a non-inversion input terminal connected to a reference voltage source 2, a transmission circuit 4 connected to the amplifier 3, and a transmission antenna 6.
On the other hand, a channel signal receiver B arranged on a receiver side, as shown in FIG. 4, includes a receiving antenna 7, a receiving circuit 8 having an input terminal connected to the receiving antenna 7, a channel decoder 9 connected to the receiving circuit 8 having a first channel signal output terminal 9a, and a drive control circuit 10 connected through the output terminal 9a to the channel decoder 9 having a braking-forward command signal terminal 10a and a forward command signal terminal 10b, which are connected to a control terminal of a braking amplifier 11 and a control terminal of a forward amplifier 12, respectively. The channel signal receiver B shown in FIG. 4 is adapted to carry out only forward and braking operations, and the discrimination between the forward and the braking is carried out by the drive control circuit 10.
The amplifiers 11 and 12 are connected in series between a voltage source VB and a ground VS through a connection G therebetween. Also, a motor 13 is connected between the voltage source VB and the connection G in a manner to be in parallel to the braking amplifier 11. The channel signal transmitter A described above is in the form of a handset so that it may be portable, whereas the channel signal receiver B is incorporated in a model car.
In the remote control of a model car, when the control element 1a is operated to slidably move the slider element 1b, a ratio of resistivity between an upper portion of the slider element 1b and a lower portion thereof is varied, which causes an operation voltage S1 supplied to the inversion input terminal of the operational amplifier 3 to be varied. In response to such a variation, a voltage supplied from the reference voltage source 2 to the inversion input terminal of the operational amplifier 3 is subtracted from the operation voltage S1 in the operational amplifier 3 to produce a difference therebetween, which is then amplified and supplied in the form of a command signal S2 to the transmission circuit 4. Subsequently, the command signal S2 is subjected to a signal treatment such as modulation, a channel multiple treatment, power amplification or the like which is general in channel multiple radiocommunication. The treated command signal S2 is allotted to, for example, a first channel signal and carried on a main carrier so as to supply in the form of radio wave from the transmission antenna 6.
FIG. 6 shows relationships between the amount of operation of the control element 1b and the command signal S2 which are obtained during the operation described above. More particularly, when the control element 1b is upwardly moved in FIG. 3 to increase the operation voltage S1, the command signal S2 tends to be increased in positive polarity so that a forward command region may be formed as indicated P in FIG. 6.
In this instance, when the control element 1b is moved to a mechanically central position in its operation range, the command signal S2 is rendered zero if a voltage of the reference voltage source 2 is determined to be 1/2 VB. Then, an electrically neutral region is realized at the mechanically central position as indicated at Q in FIG. 6.
Whereas, when the control element 1b is downwardly moved in FIG. 3 to decrease the operation voltage S1, a polarity of the command signal S2 is changed to a negative side and the negative polarity tends to be decreased. Then, a braking-backing command region is formed as indicated at R in FIG. 6.
The receiving circuit 8 of the channel signal receiver B which receives through the receiving antenna 7 radio wave on which the command signal S2 varied as described above depending upon the amount of operation of control element 1b subjects the command signal S2 to a signal treatment such as detection or the like which is general in radiocommunication. Then, in the subsequent channel decoder 9, the command signal S2 is subjected to a further signal treatment which is general in a channel multiple treatment so that a specific channel may be extracted from multiple channels to take out the first channel signal.
Thus, the command signal S2 transmitted as the first channel signal from the channel signal transmitter A is reproduced as it is in the channel signal receiver B, and then supplied to the drive control circuit 10. This causes the drive control circuit 10 to discriminate a polarity of the demodulated command signal S2. When it is determined that the command signal S2 is in a positive polarity region as indicated at P in FIG. 6, a forward command signal S3 is supplied from the forward command signal terminal 10b to the control terminal of the forward amplifier 12 and then amplified in the amplifier 12 to cause a normal rotation drive current il to be flowed from the voltage source VB through the motor 13 to the amplifier 12 and then escaped to the ground VS. This causes normal rotation of the motor 13, which results in forward movement of the model car.
Whereas, when the demodulated command signal S2 is in a negative polarity region as indicated at R in FIG. 6, the drive control circuit 10 supplies a braking-backing command signal S4 through the braking-backing command signal terminal 10a to the control terminal of the braking amplifier 11 and amplified therein. As a result, a braking current i2 corresponding to the amplified command signal S4, as indicated at dotted lines in FIG. 4, flows from the motor 13 to the amplifier 11 in the counterclockwise direction in FIG. 4 and then returns through the connection G to the motor 13. This causes braking of the motor 13, which results in the model car being stopped.
The circuit of the type which carries out normal rotation or braking of the motor 13 in response to any one of the forward command signal S3 and braking-backing command signal S4 supplied from the drive control circuit 10 as described above has been exclusively used for the conventional model racing car. The channel signal transmitter A for this purpose is generally constructed in such a manner that a range of operation of the control element 1b, as indicated at X2 in FIG. 6, is deviated in the upward direction (right direction in FIG. 6) in relation to the electrically neutral region indicated at Q in FIG. 6. This causes the backing command signal region which is unnecessary to be deleted and the forward command region to be substitutedly increased so that the control performance may be improved.
In general, the manner of control is variable depending upon an object model or object equipment, for example, a model racing car of which a speed is enjoyed by an operator, a model ordinary car of which movement is enjoyed by an operator and a model buggy car which is adapted to be operated off-road. In the model racing car, it is required to widely determine an adjustable range of a forward speed and backing is hardly required. Accordingly, it is merely necessary to provide the model racing car with forward and stop (braking) functions. On the contrary, the model ordinary car and buggy car each are required to have a backing function as well as forward and braking functions.
Thus, the motor control device requires the drive control circuit 10, the braking amplifier 11 and the forward amplifier 12 which are different depending upon a type of the model car. For example, the model buggy car or ordinary car is required to have a backing function as well as a braking function. Accordingly, the channel signal transmitter A includes the control element 1b having an operation range which is symmetric with respect to the electrically neutral region as indicated at X1 in FIG. 6. Also, the channel signal receiver B to be incorporated in the model car is required to have a circuit structure which is constructed to discriminatively distributes the braking-backing command signal into a braking command signal and a backing command signal and separately execute both signals.
An example of such a circuit structure is shown in FIG. 5. A braking-backing command signal terminal 10a of a drive control circuit 10 is connected to a control terminal of a braking-backing amplifier 11A substituted for the braking amplifier 11 in FIG. 4 and is branched on the way to be connected through a low pass filter 14 to one end of an exciter coil 15a of a relay 15, the other end of the coil 15a being connected to a ground VS. The relay 15 has a movable contact 15c, a brake contact 15b and a make contact 15m connected to one end of the motor 13, a voltage source VB and the ground VS, respectively. The remaining of the circuit of FIG. 5 is constructed in substantially the same manner as that shown in FIG. 4.
The circuit of FIG. 5 functions in substantially the same manner as that of FIG. 4 in connection with a forward command signal S3 generated during remote control of the model buggy car, and the buggy car moves forward. Whereas, when the control element 1b of the channel signal transmitter A is moved downwardly or in the left direction in FIG. 6 to supply the command signal S2 of the braking command region occupying an area in proximity to the electrically neutral region in the braking-backing command region R to the channel signal receiver B as indicated at R1 in FIG. 6, the control terminal of the braking-backing amplifier 11A receives a braking-backing command signal S4a from the braking-backing command signal terminal 10a of the drive control circuit 10 to render the braking-backing amplifier 11A operative. This causes a braking current i2 to be flowed through the brake contact 15b of the relay 15 which is still kept at a non-excitation state to the motor 13 in the counterclockwise direction as indicated at dotted lines in FIG. 4 and then returned through the braking-backing amplifier 11A to the motor 13. This leads to braking of the motor 13, resulting in the model buggy car being stopped.
When the control element 1b of the channel signal transmitter A is moved upwardly or in the left direction in FIG. 6, the sliding point is moved toward the backing command region R2 positioned below the braking command region R1 or in the left direction in FIG. 6 to reach a boundary point T between both regions R1 and R2. When a boundary command signal S2T corresponding to the point T to be supplied to the channel signal receiver B, the braking-backing command signal S4a which has been supplied from the braking-backing command signal terminal 10a of the drive control circuit 10 through the low pass filter 14 to the exciter coil 15a of the relay 15 reaches a lever of a backing command signal S4b selected corresponding to the boundary command signal S2T. Then, the relay 15 is transferred to an excited state through the exciter coil 15a after the low pass filter 14 provided the signal S4a with some delay time.
This causes the movable contact 15 to jump up to the make contact 15m to form a ground circuit on the voltage source VB side of the motor 13 so that a reverse rotation drive current i3 may be flowed from the voltage source VB through the braking-backing amplifier 11A which is rendered operative due to the supply of the command signal at a level of the backing command signal S4b to the control terminal thereof to the motor 13 in the direction opposite to a normal rotation drive current i1 as indicated at phantom lines in FIG. 5 and then flowed through the closed make contact 15m to the ground.
This leads to the reverse rotation of the motor 13, resulting in backing of the model buggy car.
During the operation, the low pass filter 14, even when the control element 1b is moved from an upward forward command region P to the downward backing command region R2 with a high speed, holds the movable contact 15c at the brake contact 15b for a period of time corresponding to the delay action to cause the flow of the braking current i2, to thereby ensure the braking action. Subsequently, the reverse rotation drive current i3 is flowed through the motor 13 to carry out the reverse rotation of the motor 13 to smooth the switching operation between the forward and the backing. More particularly, the drive control circuit 10 shown in FIG. 5 is adapted to generally separate the control mode of a controlled object into two modes, namely a forward mode and a braking-backing mode, and the discrimination therebetween is carried out by the drive control circuit 10.
Also, the drive control circuit distributes the braking-backing mode to a braking mode and a backing mode. This is carried out by introducing a signal obtained due to the selection of the braking-backing mode in the drive control circuit 10 to the low pass filter 14 to carry out the switching between the braking and the backing depending upon a magnitude of the braking-backing signal. In FIG. 5, the low pass filter 14 acts as a kind of an integrator or capacitor, which is adapted to substantially fail in the generation of an output when the braking-backing output is small and generate an output sufficient to excite the coil of the subsequent relay when it is increased.
However, this causes a level of the switching between the braking and the backing to be unconditionally determined by the low pass filter 14. Accordingly, it is impossible to determine the switching level depending upon a type of a controlled object.
As described above, in the conventional motor control device, the channel signal receiver B must be varied in a circuit structure depending upon a type of the model car, because the model car is divided into a type such as a model racing car which is not required to have a backing function and a type such as a model buggy car which is required to have it. Accordingly, the conventional motor control device has a disadvantage that the manufacture and inspection steps and inventory management are highly troublesome.
Also, in the conventional device, the discrimination as to whether the braking-backing command signal S4a is increased to a level of the backing command signal S4b in the drive control circuit 10 within the channel signal receiver B is fixedly determined depending upon an intrinsic electrical performance of the relay 15 having the level transferred to an excitation state of the relay 15 or the movable contact 15c contacted with the make contact 15m. Therefore the boundary command signal S2T, a boundary point T between the braking command region R1 and the backing command region R2, and a boundary position xT corresponding thereto is also fixedly determined.
When the channel signal transmitter A in which a range of operation of the control element 1b is deviated to be suitable for use for the model racing car as indicated at X2 in FIG. 6 is to be used for the remote control of the model buggy car, the boundary position xT of the control element 1b is determined at an end of the operation range X1 to cause the backing command region X2 to be excessively decreased, resulting in a control performance in the backing being highly deteriorated. Accordingly, the channel signal transmitter A to be operated by an operator must be selected depending upon a type of the model car.